Conventional location-specific information systems are used to provide locally relevant information. For instance, a business establishment may play a recording announcing the goods or services that the establishment provides. Similarly, many museums have sound recordings that correspond to exhibits. These systems must be sufficiently spatially separated such that the audio signals do not interfere with one another. One proposed approach to preventing interference is to provide headphones at various locations. This approach has the advantage of allowing users to start the message when they arrive and in some cases even to select the language of the message. Such systems often require a significant infrastructure, and in some systems it is quite difficult to change the message.
Other current systems for delivering localized information to users rely on low power AM radio signals. Such systems are commonly used with respect to traffic and road conditions. This approach, while having much simpler requirements than the systems referred to above, suffers from additional significant drawbacks. First, such an approach is not location specific, but rather likely covers a fairly broad geographical area. Accordingly, the radio system likely delivers a general message applicable to the entire coverage area, and the listener may need to listen to an entire lengthy message in order to obtain the desired specific information. Furthermore, meteorological variations can impact both the area of coverage and quality of the radio signal.
Existing location-specific information systems do not enable real time access to evolving location-specific information and do not enable users to add new information. In addition, currently utilized location-specific information systems which track the user's position either require significant external infrastructure to facilitate user tracking or rely on very coarse position information, such as that obtained from a cellular phone. Presently a need exists for a system that enables users to access embedded information attached to a specific location by another user. Further, there is a need for a system that is capable of providing real time placement of annotations at various locations in the user's environment.